Can Super Chlorinating With Bleach Be Used To Shock A Swg Pool?

[Gavin]

When I refer to "active chlorine" I am referring to the hypochlorous acid concentration since that is what does the sanitation and most of the oxidation. The chlorine bound to CYA (technically called chlorinated isocyanurates) are minimally effective sanitizers and oxidizers (about 100 times slower than hypochlorous acid as far as oxidation of a standard organic as described here). At a pH of 7.5, the 7.5 ppm FC with 100 ppm CYA there is only 0.031 ppm as hypochlorous acid, 0.033 ppm as hypochlorite ion, and 7.436 ppm as a variety of different chlorinated isocyanurate compounds (that is, chlorine bound to CYA). This has roughly the same oxidation and sanitation power as having only 0.07 ppm FC with no CYA.

In other words, when you have CYA in the water, there is very little real chlorine available doing the real work, but fortunately most pathogens need only a very low concentration of chlorine to get killed quickly. Most of the chlorine is in reserve and will get released from being bound to CYA as the active real chlorine gets used, but reaction rates are based on the hypochlorous acid concentration and not on the amount in reserve. You can read the introductory sections of the classic 1974 paper that defined the equilibrium constants between hypochlorous acid and the chlorine bound to CYA here.

Thanks chem for clearing that up. but how did you figure out the hypochlorous acid and hypochlorite ions figures? is there a formula?

[chem geek]

The equilibrium constants for the multiple simultaneous chemical equations are described in the link I gave to the O'Brien paper from 1974. I put all of that into a spreadsheet here, but this is not for novice users. It turns out that there are rough rules-of-thumb you can use where the equivalent FC with no CYA is approximately equal to the FC/CYA ratio, at least at cooler pool temperatures and near a pH of 7.5 (I derive this rule-of-thumb in this post).

However, there really isn't a need for you to calculate the hypochlorous acid or hypochlorite ion concentrations. Just remembering the FC as a % of CYA is sufficient or you can use a table such as this one that is based on these principles.

[Gavin]

The equilibrium constants for the multiple simultaneous chemical equations are described in the link I gave to the O'Brien paper from 1974. I put all of that into a spreadsheet here, but this is not for novice users. It turns out that there are rough rules-of-thumb you can use where the equivalent FC with no CYA is approximately equal to the FC/CYA ratio, at least at cooler pool temperatures and near a pH of 7.5 (I derive this rule-of-thumb in this post).

However, there really isn't a need for you to calculate the hypochlorous acid or hypochlorite ion concentrations. Just remembering the FC as a % of CYA is sufficient or you can use a table such as this one that is based on these principles.

Thanks Chem. yes I was thinking I really wouldn't need to calculate active chlorine as I usually calculate the % of CYA and that keeps my pools nice and clear. Just thought someone might say one day that 8ppm was a hell of a lot of FC to keep in a pool but when the CYA is 100ppm and the owner doesn't want any water drained and pool refilled what can you do? Just thought the active chlorine number might put their mind as ease and realize the pool was still safe to swim in even at 8ppm.

[Swim 'N Save USA]

The equilibrium constants for the multiple simultaneous chemical equations are described in the link I gave to the O'Brien paper from 1974. I put all of that into a spreadsheet here, but this is not for novice users. It turns out that there are rough rules-of-thumb you can use where the equivalent FC with no CYA is approximately equal to the FC/CYA ratio, at least at cooler pool temperatures and near a pH of 7.5 (I derive this rule-of-thumb in this post).

However, there really isn't a need for you to calculate the hypochlorous acid or hypochlorite ion concentrations. Just remembering the FC as a % of CYA is sufficient or you can use a table such as this one that is based on these principles.

Thanks Chem. yes I was thinking I really wouldn't need to calculate active chlorine as I usually calculate the % of CYA and that keeps my pools nice and clear. Just thought someone might say one day that 8ppm was a hell of a lot of FC to keep in a pool but when the CYA is 100ppm and the owner doesn't want any water drained and pool refilled what can you do? Just thought the active chlorine number might put their mind as ease and realize the pool was still safe to swim in even at 8ppm.

for easy use and future reference, using a test kit and the "pool calculator" will help you greatly in balancing your swimming pool. They also have a handy application available for the iphone and ipod touch.

[Gavin]

The equilibrium constants for the multiple simultaneous chemical equations are described in the link I gave to the O'Brien paper from 1974. I put all of that into a spreadsheet here, but this is not for novice users. It turns out that there are rough rules-of-thumb you can use where the equivalent FC with no CYA is approximately equal to the FC/CYA ratio, at least at cooler pool temperatures and near a pH of 7.5 (I derive this rule-of-thumb in this post).

However, there really isn't a need for you to calculate the hypochlorous acid or hypochlorite ion concentrations. Just remembering the FC as a % of CYA is sufficient or you can use a table such as this one that is based on these principles.

Thanks Chem. yes I was thinking I really wouldn't need to calculate active chlorine as I usually calculate the % of CYA and that keeps my pools nice and clear. Just thought someone might say one day that 8ppm was a hell of a lot of FC to keep in a pool but when the CYA is 100ppm and the owner doesn't want any water drained and pool refilled what can you do? Just thought the active chlorine number might put their mind as ease and realize the pool was still safe to swim in even at 8ppm.

for easy use and future reference, using a test kit and the "pool calculator" will help you greatly in balancing your swimming pool. They also have a handy application available for the iphone and ipod touch.

Thanks. yes I like using the pool calculator. want to get an itouch and the app.